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Graptolites

Facts

  • Scientific classification: Pterobranchia (class), Graptolitina (subclass)
  • Epoch: Cambrian to Carboniferous (542 to 318 mya)
  • Conservation status: Extinct
  • Cause of extinction: Many species went extinct from climate change
  • Fun fact: They are widely used for stratigraphic correlation

Additional sources: Britannica, Wikipedia

Image source: Science Source

Luck was not on the side of the highly successful ammonites. Rewind the evolutionary clock even further to what is considered the first of the world’s mass extinction events during the Ordovician period, and many graptolites fared no better. Prior to the Ordovician extinction, which is hypothesized by many to be caused by a glaciation event brought on by climate change, V-shaped graptolites were predominant, and clearly successful. After the extinction event, they were gone from the fossil record. This again shows that under extenuating circumstances, different rules apply.

Kolbert also chose the graptolites to demonstrate another point, specifically that there is no single cause of mass extinctions. After the discovery of the K-Pg asteroid crater, people began to wonder if every mass extinction event was caused by impacts. But there was no evidence for other impacts that could be found, and it is unfortunately not that simple. Instead, the demise of the V-shaped graptolites was caused by climate change, a cause of extinction that is especially pertinent to us right now. Our reshaping of the world ecosystem and the climate has led to Paul Crutzen branding of a new name for our current epoch. We are no longer in the Holocene but the Anthropocene. What’s most worrisome is that our impact on the climate has occurred to a greater degree in a comparatively infinitesimal amount of time What species will end up like the V-shaped graptolites?

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